Updated GitHub actions to run only on changed markdown files

Author: eshanrnh

.github/workflows/check-pr-links.yml

@@ -1,16 +1,75 @@
-name: Check Links
+name: Check Links In Pull Requests
 
 on:
   pull_request:
-    types: [opened, synchronize, reopened]
+    branches:
+      - main
+    paths:
+      - '**/*.md'   # Only trigger workflow if any Markdown files change
 
 jobs:
   check-links:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: lycheeverse/lychee-action@v2
-      - name: Comment Broken Links
-        uses: marocchino/sticky-pull-request-comment@v2
+      # Step 1: Checkout the repository
+      - name: Checkout GitHub repo
+        uses: actions/checkout@v4
         with:
-          path: lychee/out.md
+          fetch-depth: 0
+
+      # Step 2: Check out base branch and dump all links (no fragments)
+      - name: Check out base branch
+        run: git checkout ${{ github.event.pull_request.base.ref }}
+
+      - name: Dump all links from base branch (no fragments)
+        uses: lycheeverse/lychee-action@v2
+        with:
+          args: "--dump ."
+          output: ./existing-links.txt
+        continue-on-error: true
+
+      # Step 3: Stash untracked files and switch back to feature branch
+      - name: Stash untracked files
+        run: git stash push --include-untracked
+
+      - name: Check out feature branch
+        run: git checkout ${{ github.head_ref }}
+
+      - name: Apply stashed changes
+        run: git stash pop || true
+
+      # Step 4: Add base branch links to .lycheeignore
+      - name: Update ignore file
+        run: |
+          if [ -f "existing-links.txt" ]; then
+            cat existing-links.txt >> .lycheeignore
+          fi
+
+      # Step 5: Get changed Markdown files in the PR
+      - name: Get changed Markdown files
+        id: changed-files
+        run: |
+          files=$(git diff --name-only origin/${{ github.event.pull_request.base.ref }} ${{ github.head_ref }} | grep '\.md$' || true)
+          echo "changed_files=$files" >> $GITHUB_ENV
+
+      # Step 6: Run Lychee on changed files only (with fragments)
+      - name: Run Lychee link checker
+        uses: lycheeverse/lychee-action@v2
+        with:
+          args: "--no-progress --include-fragments ${{ env.changed_files }}"
+
+      # Step 7: Provide a helpful failure message
+      - name: Helpful failure message
+        if: ${{ failure() }}
+        run: |
+          echo "::error::Link check failed! Please review the broken links reported above."
+          echo ""
+          echo "If certain links are valid but fail due to:"
+          echo "- CAPTCHA challenges"
+          echo "- IP blocking"
+          echo "- Authentication requirements"
+          echo "- Rate limiting"
+          echo ""
+          echo "Consider adding them to .lycheeignore to bypass future checks."
+          echo "Format: Add one URL pattern per line"
+          exit 1